1. Field of the Invention
The present invention relates to a rotating signal generator apparatus having a signal generator such as a sine encoder for producing a signal whose frequency is proportional to the rotational speed of a rotor and whose rising and falling angles near points crossing zero become larger with the rotating speed of the rotor. The apparatus generates the rotating signal of the rotational speed, the rotational position or the like.
2. Description of the Prior Art
It has been proposed in the official gazette of Japanese Patent Application Laid-open No. 57-175259 that an angle signal transducer for producing a first signal of a magnitude corresponding to the rising and falling angles of the output of the signal generator as stated above, and a frequency transducer for producing a second signal of a magnitude corresponding to the frequency of the output of the signal generator are provided to derive the rotating signal of the rotor by using the first signal in a low speed range and the second signal in a high speed range.
As shown in FIG. 2, the magnitude of the first signal exhibits a characteristic in which it is properly proportional to the rotational frequency of the rotor in the low speed range, but it becomes unproportional in the high speed range.
To the contrary, the magnitude of the second signal is properly proportional in the high speed range but is unproportional in the low speed range as illustrated in FIG. 3.
Accordingly, it is very effective for generating the rotating signal that the first and second signals are switched midway and then used as disclosed in the official gazette of Japanese Patent Application Laid-open No. 57-175259.
With the prior-art apparatus, however, there has been the problem that in switching the first signal to the second signal or vice versa, the rotating signal generator apparatus does not produce its output signal for a period of time.
It is of course possible to incorporate a capacitor for the purpose of sustaining the signal at the switching. This measure, however, worsens a quick response characteristic undesirably.